Rotary instrument brake



March 2, 1965 J. W. IHRIG ROTARY INSTRUMENT BRAKE Filed Aug. 28,

lZm 28% K /2." lab R FIG. 9 h l/ /R \V INVENTOR. JEROME 14 JHR/a United States Patent 3,172,071 ROTARY INSTRUNLENT BRAKE Jerome W. Ihrig, Riverside, Calif., assignor to Bourns, Inc., a corporation of California Filed Aug. 28, 1962, Ser. No. 219,864 Claims. (Cl. 338-163) The invention herein disclose-d pertains to rotary instruments such as variable resistors or potentiometers, of the types that are attached to and project from the front face of a panel, and more particularly the invention pertains to simple means for permitting ready arrestment or locking and releasing of the rotary means such as the rotary housing that is actuated to change the adjustment of the instrument.

In a variable resistor device presently known in the art, the operative electrical components including a plural-turn helical resistance element are enclosed within a generally cylindrical shell that is rotatably supported upon stationary means comprising a flanged stud that is adapted for mounting in an aperture formed in a panel or console. The variable resistor device is disposed at the front of the panel and is constructed and arranged to be adjusted by rotation of the shell which serves both as an adjusting knob and as a principal housing member for protecting the other components of the resistor. A preferred form of a described variable resistor device comprises a clock-type dial indicator positioned at the outer (front) end of the shell, for indicating the number of full turns and fraction of a turn through which the shell has been rotated from an initial or zero position. Since in many instances a plurality of such variable resistor devices may be mounted in close juxtaposition, or closely adjacent to other devices that require manual adjustment or operation, there is likelihood of a hand of a technician, or of a tool, coming inadvertently into contact with the knob or shell and accidentally rotating the rotatable electrical component of the resistor to an undesired position. Such accidental misadjustment is especially likely because of the ease with which the shell of the described device may be rotated, application of only a very light tangential force on the shell being suificient to cause rotation.

The present invention provides an inexpensive readily operated brake device or means that permits an operator to secure or lock the rotatable shell or knob against rotation, or to release the shell for rotation. The brake device is so made that it occupies very little space beyond that small space required for the resistor device, and is so constructed that the operating member thereof can be readily operated by one or more fingers of an operator or by means of a simple tool such as a pencil and eraser. In the commercial form of the previously described variable resistor device a special anti-rotation washer is employed to prohibit rotation of the mounting stud in the aperture of the panel. The washer comprises first and second oppositely directed key members bent out from the body of the washer. The first key reposes in a small hole formed in the panel, and the second fits in a small hole formed in a stationary part of the body of the potentiometer, whereby relative rotation is prevented. In a preferred embodiment of the present invention the anti-rotation washer is somewhat modified and is used as one member of the brake device. The washer is provided around its periphery with a bead or flange to provide a circumferentially existing brake element, the edge surface of which is disposed closely adjacent to an annular rear end surface of the rotary shell for frictional engagement with that surface. Thus when the brake element is pressed forwardly as by cam means, engagement with the annular surface of the shell occurs, and the latter is arrested or frictionally locked 3,172,071 i atented Mar. .2, 1965 against rotation until the brake element is released. The arrangement is such that any degree of drag or locking effect can be produced, from a slight frictional drag to effective locking.

For the purposes of accommodating the present invention a small additional length of the supporting stud of the instrument is provided for a seat upon which an inner flange of the anti-rotation washer is disposed. The flange provides a seat upon which the brake-operating means of the invention is mounted. The brake-operating means is in the preferred embodiment an integral single-piece device arranged for limited rotary or rocking movement on the seat formed on the washer, and is provided with one or more cam elements each of which is disposed and arranged for cooperative action with a respective surface element of the washer. The preferred brake-operating device, hereinafter referred to as the brake actuator, is essentially a cup-shaped device, the bottom of which is perforated with an aperture of the proper size so it seats for rotation upon the step or seat formed on the washer immediately behind the body of the washer and forwardly of the flange of the stud, and the cylindrical portion of which closely encircles a rear portion of the sleeve of the variable resistor but is spaced outwardly therefrom a small distance to provide radial clearance. The disc-like bottom or rear part of the cup-like actuator is provided with cam surfaces disposed to rotatively coact with respective ones of the surface elements provided on the washer. The cam surfaces may be provided in any suitable way, and for example may be provided by piercing or lancing and offsetting small portions of the bottom of the cup-like actuator. Each cam surface or cam thus provided is preferably inclined so as to produce a wedging action on a respective washer surface when the actuator is rotated or rocked in one direction, to apply the brake or lock, and the relieve the braking or locking effect when thereafter rotated in the opposite direction. The cams preferably are so formed that they are resilient so they continue to act despite vibration of the instrument. While a single surface element and a single cam suffice to provide an adequate amount of braking or locking action, for balanced mechanical action it is preferred that an even number of cams be provided in the cam or actuator and a corresponding number of surface elements be provided in the brake means or disc. From the preceding description it is evident that when the cup-like actuator is rocked in one direction to engage the brake or lock, the cam-element means of the actuator resiliently deform and force the rim of the brake means or washer into engagement with the rotary shell or sleeve of the potentiometer to arrest the movable parts thereof; and when rocked reversely the cam-element means move away from the brake means and the latter by inherent resilience springs rearwardly away from the sleeve to release the movable parts for free movement. The actuator preferably is inexpensively produced by drawing and stamping from a sheet of suitable material, but may be made by casting or molding. Due to the thinness of the bottom (rear) portion of the actuator and of the flanges of the Washer or brake disc, the device of the invention adds only a negligible amount to the space required for the entire resistor device.

The preceding brief general descriptive sketch of the invention makes it evident that it is a principal object of the invention to provide improvements in instruments such as rotary variable resistors of the aforementioned type in which the instrument is adjusted by rotation of a shell or the like.

Another object of the invention is to provide a simple brake or arrestment device for a rotary instrument of the I type mentioned.

Another object of the invention is to provide an inexpensive arrestment device for a rotary instument of the type mentioned.

Another object of the invention. is to provide a brakeoperating device that does not add appreciably to the space requirements of a rotary potentiometer or like instrument.

Other objects of the invention, and advantages thereof, will be made apparent in the appended claims and by the following description of a preferred form of the invention as illustrated in conjunction with a rotary potentiometer in the accompanying drawings that form a part of this specification.

In the drawings:

FIGURE 1 is a side view of a panel mounted potentiometer of the type having the operating components enclosed in a knob-like shell, with parts broken away and partly in section to disclose details;

FIGURE 2 is a view in section taken as indicated by line 22 in FIG. 1;

FIGURE 3 is a face view of a washer or brake disc comprised in the structure depicted in FIG. 2;

FIGURE 4 is a distorted view in section of the component depicted in FIG. 3, taken as indicated by line 4-4 in FIG. 3;

FIGURE 5 is a face view of the inner side of a brakeoperating component illustrated in side elevation in FIG. 1;

FIGURE 6 is a distorted view in section taken as indicated in FIG. 5;

FIGURE 7 is a detail view of fragmentary portions of a potentiometer, a brake member, and a brake-operating member depicted in part in FIG. 1 in disassembled array;

FIGURE 8 is a view taken as indicated by line 8-3 of FIG. 1; and

FIGURE 9 is a fragmentary sectional view taken as indicated by line 99 of FIG. 8 and illustrating engagement of the cam means with the brake means to cause the brake means to arrest the potentiometer.

Referring to the drawings, and first to FIG. 1, a variable resistor or potentiometer indicated generally at R is afiixed to a panel P. The potentiometer comprises a flanged and threaded supporting stud S, the flange F of which is drawn against the front face of the panel by the action of washer W and nut N which is received on the thread of the stud and is turned up tightly to hold the potentiometer in place. The rear end of the stud is received through an aperture of appropriate size formed in the panel. As shown in FIG. 6 the flange F has been removed from the stud, but it will be understood that it is in fact an integral portion of the stud. The potentiometer also comprises an inner stationary body part B which is fixedly mounted on the stud, and a rotatable barrel or shell H which encloses operating parts of the potentiometer and serves when rorated to effect changes of resistance between certain terminals of the potentiometer. Internally the potentiometer may be like or similar to that disclosed in US. Patent 3,069,646. Shell H has an annular rear end face I-If (FIG. 9) which in the disclosed embodiment of the invention is disposed in a plane and hence is flat.

As is indicated in FIG. 1, the potentiometer body is prevented from rotating by a pin K which enters into a small hole provided in panel P, and into a small hole provided in body B. Pin K is rigidly mounted in an aperture extending through a washer or brake member 10 that is received on stud S between flange F and body B. Member 10, as indicated in FIGS. 3 and 4, is washer-like in form, but has a rearwardly-extending inner flange or collar 16a and an outer forwardly-extending flange 10b. Inner flange or collar 10a has an outer surface 106 that is suitably formed to provide a seat or bearing surface for a purpose presently explained. Additionally, the outer flange is provided with an annular forward face Itld' arranged and dimensioned for faceto-face contact and cooperation with the aforementioned annular rear end face Hf of sleeve H.

41 Further, member If? is provided with a plurality (two, as depicted) of openings 10m, 1911, spaced radially from the inner flange 10a, as shown.

As is indicated in FIGS. 1 and 7, member 1% supports for rotation on surface a cup-like brake actuator 12 which has a radial bottom (rear) portion 12b and a generally cylindrical forwardly extending rim portion 12. The actuator has an axial aperture formed as a bearing surface for close fitting but easy rotative coaction with member 10. Actuator 12 further is provided with a slot 12s (FIGS. 5 and 6) through which anti-rotation pin K extends. As is evident, pin K thus conveniently serves as a stop device in conjunction with the ends of the slot, to limit rotative movements of the actuator.

Formed by piercing and die action in the bottom of the actuator are first and second resilient cam devices 12m and 1211, each constructed and arranged in proper respective positions to normally extend into respective ones of the openings ltim, Itin formed in brake member fit. The relative arrangement of the components It and 12 and stationary components including stud S with flange F, and body B, that with the cam devices disposed wholly within and immediately behind openings lldm, 1911, there is a small clearance between the rear end of sleeve H and the front face or brake surface 19d of member It); and there is also a small clearance between the rear face of member 10 and the front face of the bottom of member 12. Thus member 12 may be rotated, but as rotation proceeds in one direction the projecting ends of the cams engage respective ends of openings 10m and film, and rotation is halted. As rotation of the actuator 12 proceeds in the opposite direction the inclined forward faces of the cams ride over respective endwall portions at the ends of openings film and 1011, forcing member 12 into firm contact with flange F and forcing brake member lit forwardly into engagement with the rear end surface H of sleeve H. Continued rotation of actuator 12 causes additional stressing of the resilient cams and increase of braking force applied to the sleeve H. The relative positions of the parts may then be as is indicated in FIGS. 8 and 9, wherein it may be noted that cam 12m, for example, is stressed partly back into the opening from which it was lanced, and is by that action pressing forwardly on brake member It) and forcing the rim of the latter into face-to-face engagement with face H of sleeve II. Since brake member Iii is restrained from rotation by engagement of pin K in the panel P and body B, sleeve H is frictionally locked in any position into which it may have been adjusted. Further, since there is no application of force tending to rotate shell H by member 10, the adjustment of the shell and operating parts of the potentiometer is not disturbed.

The preceding description of a preferred embodiment of the invention makes it evident that the objects of the invention have been attained. In the light of the disclosure it is evident that modifications will occur to those skilled in the art and accordingly it is not desired that the invention be limited except by the appended claims.

I claim:

1. A variable resistor comprising:

first means, including a stud adapted to be secured to a panel andextend forwardly therefrom, and rotary resistor-adjusting means mounted on said stud for rotation thereon, said resistor-adjusting means comprising a rearwardly-facing circular surface;

second means, including a non-rotatable means supported at the rear of said rotary resistor-adjusting means and comprising a brake element encircling said studand having braking surface means arranged for engagement with said rotary resistor-adjusting means at at least a plurality of areas uniformly spaced around the periphery of said circular surface and movable from a rearmost position forwardly into braking engagement with said rearwardly-facing surface; and

third means, including a device rotatably supported 5 rearwardly of said non-rotatable means and including a plurality of resilient cam means uniformly spaced around said device said cam means being constructed and arranged to engage and move said brake element forwardly into braking engagement with said surface incident to rotation of said device in one direction, and to permit said braking element to move rearwardly out of engagement with said surface incident to rotation in the opposite direction.

2. Brake device means for a panel-mounted knobadjusted rotary instrument having support means adapted to extend forwardly of the mounting panel, comprising, in combination with the rotary adjusting means of the instrument:

a disc-shaped brake member disposed on said support means at the rear of said adjusting means and having an annular series of braking surface elements spaced around a periphery of the brake member, and means for holding said member against rotation;

and a single-piece rotary brake actuator disposed at the rear of said brake member and having resilient cam means thereon movable relative to the actuator and effective when rotated to move said member forwardly to move said braking surface elements into frictional locking engagement with said rotary adjusting means, whereby to effectively lock the latter means against rotation.

3. A variable resistor comprising:

a stationary panel-mounted support means;

variable resistor means supported on said support means forwardly of the panel mounting and including an outer rotatable knob-like means for effecting adjustment of the resistive value exhibited by the resistor;

a member supported by said support means at the rear of said rotatable knob-like means and encircling said support means and having an annular series of braking surface means uniformly spaced therearound and disposed to be moved forwardly to bring said braking surface means into frictional contact with the knob-like means;

and a rotary brake actuator disposed rearwardly of said stationary member and comprising resilient cam means effective upon rotation of said actuator to move said member forwardly into frictional engagement with said rotatable means,

whereby to provide a simple locking brake for the Variable resistor.

4. A two-piece brake device for an instrument having a knob-like rotary adjustment element, comprising:

a washer-like brake member disposed transversely of the axis of the rotary adjustment element at the rear of the latter and having at least diametrically opposite portions thereof constructed and arranged to be moved forwardly into frictional contact with a rearwardly facing surface of said rotary adjustment element; and

a thin sheet-like brake-actuator device disposed rear- 'wardly of said brake member and having resilient means effective upon rotation of the actuator to force said brake member forwardly to move said diametrically opposite portions thereof into frictional contact with said rotary adjustment element.

5. A two-piece brake device for an instrument having operative components housed in a generally cylindrical shell-like rotary housing member having a rearwardly facing surface and arranged for manual rotation to effect adjustment of the instrument and having a centrallydisposed supporting member arranged to support the operative components and to be mounted on the front face of a panel to extend forwardly thereof, comprising:

a washer-like brake member disposed coaxially with and at the rear of said housing member with an annular series of braking portions thereof closely adjacent the rearwardly facing surface of said housing 5 member and said brake member being constructed and arranged to be moved forwardly to bring said braking portions into frictional engagement with said surface, and means restraining said brake member against rotation; and

a rotatable brake-actuator arranged generally coaxial with said housing member and having uniformly spaced-apart resilient cam means constructed and arranged to move said brake member forwardly incident to rotation of the actuator in a predetermined direction, whereby rotation of said brake-actuator in said direction is effective to cause said brake member to frictionally lock said housing member against rotation.

6. A variable instrument comprising:

support means adapted to be mounted in an aperture in a panel and extend forwardly therefrom;

a rotary knob-like housing structure adapted to enclose the operative components of said instrument, mounted for rotation on said support means and having a circular frictional surface;

a disc-like brake means, supported by said support means generally coaxial with said housing structure at the rear thereof and having a circular brake surface closely adjacent to said frictional surface; and

a brake-actuator disposed rearwardly of said brake means and having a circularly-arranged set of resilient cam devices constructed and arranged to move said brake means forwardly to move said circular brake surface into frictional engagement with the said circular frictional surface of said housing structure and to lock said brake surface against said frictional surface incident to rotation of the brakeactuator in one direction, and to release said brake means for rearward movement incident to subsequent rotation in the opposite direction.

7. A variable instrument according to claim 6, said brake means comprising a set of apertures therein spaced radially from the axis thereof, and said brake-actuator comprising said set of cam devices constructed and arranged to repose in respective ones of said apertures and to be rotated into contact with said brake means to move the latter as specified.

8. A variable instrument according to claim 6, said brake-actuator comprising a forwardly turned generally cylindrical portion extending forwardly and over at least a part of the rear end portion of said knob-like housing structure, to facilitate manual manipulation of said actuator.

9. A variable instrument according to claim 6, said brake means comprising a set of uniformly dispersed apertures and cam-follower surfaces spaced radially from the axis thereof, and said brake-actuator comprising said set of resilient cam devices each disposed in a respective one of said apertures when in inoperative disposition and arranged to be rotated into contact with a respective one of said cam-follower surfaces, and said brake-actuator comprising a cylindrical flange extending forwardly over at least the rear end portion of said housing structure to facilitate manual manipulation of said actuator.

10. A variable resistor comprising:

support means having front and rear portions and constructed and arranged to be afiixed by the rear portion thereof to a panel at an aperture in the panel and to extend forwardly from the panel;

a rotary knob-like housing structure adapted to enclose operative components of the resistor, mounted forwardly of said rear portion for rotation on said support means and having a rearwardly exposed circular set of frictional surface portions;

a disc-like brake member formed from sheet material and having a complementary annular set of brake surface portions closely adjacent said rearwardly exposed circular set of frictional surface portions;

and a movable brake-actuator disposed rearwardly of said brake means and constructed and arranged to move said brake member forwardly to bring said brake surface portions into frictional engagement with said rearwardly exposed surface incident to movement of said actuator in a first direction transversely of the direction of movement of said brake surface.

References Cited by the Examiner UNITED STATES PATENTS 2,509,058 5/50 Haury 338-162 5% 3/56 Dunkelberger et a1. 188-71 X 3/57 Iungles 18871 X 7/58 Lee 18871 4/62 Tomita 188-71 FOREIGN PATENTS 1898 Great Britain. 3/ 18 Great Britain.

10 ARTHUR L. LA POINT, Primary Examiner 

3. A VARIABLE RESISTOR COMPRISING: A STATIONARY PANEL-MOUNTED SUPPORT MEANS: VARIABLE RESISTOR MEANS SUPPORTE DON SAID SUPPORT MEANS FORWARDLY OF THE PANEL MOUNTING AND INCLUDING AN OUTER ROTATABLE KNOB-LIKE MEANS FOR EFFECTING ADJUSTMENT OF THE RESISTIVE VALUE EXHIBITED BY THE RESISTOR; A MEMBER SUPPORTED BY SAID SUPPORT MEANS AT THE REAR OF SAID ROTATABLE KNOB-LIKE MEANS AND ENCIRCLING SAID SUPPORT MEANS AND HAVING AN ANNULAR SERIES OF BRAKING SURFACE MEANS UNIFORMLY SPACED THEREAROUND AND DISPOSED TO BE MOVED FORWARDLY TO BRING SAID BRAKING SURFACE MEANS INTO FRICTIONAL CONTACT WITH THE KNOB-LIKE MEANS; AND A ROTARY BRAKE ACTUATOR DISPOSED REARWARDLY OF SAID STATIONARY MEMBER AND COMPRISING RESILIENT CAM MEANS EFFECTIVE UPON ROTATION OF SAID ACTUATOR TO MOVE SAID MEMBER FORWARDLY INTO FRICTIONAL ENGAGEMENT WITH SAID ROTATABLE MEANS, WHEREBY TO PROVIDE A SIMPLE LOCKING BRAKE FOR THE VARIABLE RESISTOR. 